In the late 1980s and 1990s, using a hodgepodge of Old English and Icelandic terms for various Orlanthi words was all the rage. Greg was deep in Pendragon, and many such terms came pretty naturally. I don’t know if anyone has ever served as the creative lead on two very different settings simultaneously, but some bleed-through is inevitable. And so we had terms like fyrd, moot, godi, carl, cottar, etc. Such terms co-existed with Latinisms such as “Rex” and later with purely fictional words as “Dar” or “Alakoringite”.
With the revival of RQ, pretty much all of that has been swept away. About the only one we’ve kept is “thane” – which literally just means “retainer, attendant, companion,” which we could also transliterate as “Lord” or “Sir,” if we felt so inclined.
We also kept “Rex” because “Orlanth Rex” is deeply ingrained in the setting and the texts. Also thanks to the dinosaur, “Rex” is pretty easily understood even in North America (and is easily translated in other languages).
“Acolyte” or “godi” became “God-talker” in part because the actual role of acolytes are played by initiates. And “godi” was both “priest” and “chieftain” (and more used for chieftain than priest in the Icelandic sagas) in God-talker is a part-time priest, found mainly in rural communities where the resources might not exist to support a full time priest.
Our mental visualization of Glorantha is shaped by the words we use to describe it. A big reason to get rid of those terms is to break the assumption that the Orlanthi are Germanic Northern Europeans. They aren’t. Those cultural elements they share with the ancient Germanics they share with plenty of other cultures – Thracians, Mycenaeans, Hallstatt Celts, Macedonians, Gandharans, Pashtuns, Mesoamericans, early Indo-Europeans, etc. “Militia” works just as well as “fyrd” and lacks the other connotations of the latter. It is also a lot easier to translate into other languages!
Now you are welcome to populate your Glorantha with fyrds, cottars, etc. I’m not going to send out out the RQ Language Police to stop you! But you are unlikely to see such terminology in Chaosium publications, and I’m less likely to want to run with a submission filled with such terms (as it requires more editorial work replacing those terms).
Please note that militia is widely used in the US beyond just 2nd amendment context. It is well established as non-professional volunteers. Hence the reason we refer to the colonial militias in the US War of Independence. Or that we refer to the tribal and city militia in WBRM.